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EVAL-AD8302-ARDZ

Hi,

I am using EVAL-ADC8302-ARDZ to make time delay measurements from the phase-difference measurements. We have downloaded and compiled the python development exe file and are running the system in a command line mode. We have added a line of code to continuously log the 'RFPower[1]' measurements into a file for later processing in an excel spreadsheet. I have two questions:

(1)  How do I go from the measured phase difference values in voltage to phase difference values in degrees?

(2) Is there a way to save my own calibration file so that I can load it whenever I take new measurements?

I appreciate in advance your thoughts/feedback on those questions.

v/r,

-Alex 

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  • Greetings Alex,

    AD8302 phase measurement uses the EX-OR method, as described on bottom of datasheet page 15. Because of this, there will be a phase ambiguity. The ambiguity is typified by the triangle shape of the phase response across 360 degrees, as shown in datasheet graphs TPC 25 to TPC 29. Typically the application will take this into account and incorporate a known provision to resolve the ambiguity. In many a basic application, the designer already knows which side of the triangle the circuit operates, thus determining which of the two equations below will apply. 

    (1) Looking at datasheet TPC 25 for example, we can write the equation below to describe the left-hand side of the triangle response: 

            phase [degrees] = -180 + (VPHS * 100)

    Similarly, we can write a similar equation to describe the right-hand side of the triangle response:

            phase [degrees] = 180 - (VPHS * 100)

    Notice the rounding of the triangle response near the peaks. It means for best accuracy, the design should avoid these areas. The equations above assume linearity, and ignore the rounding. 

    (2) There should be a small EEPROM on the AD8302-ARDZ board which a clever programmer could use to store the basic slope and offset coefficients for calibration. I don't think our factory demo supports such feature. In lieu of this technique, perhaps consider storing calibration coefficients elsewhere, such as in the Python code somewhere. 

    Hope this helps.  -Bruce H. 

  • Hi Bruce,

    Thanks you so much!

    -Alex

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